Call-signal apparatus for telephone-exchanges.



A 0 9 1 L l T C O D E T N E T A P N A E D W W 7 9 l 7 7 N 7 CALL SIGNAL APPARATUS FOR TELEPHONE EXCHANGES.

APPLICATION FILED JAN 14. 1902.

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No. 771,897. PATENTBD 007. 11, 1904. W. W. DEAN.

CALL SIGNAL APPARATUS FOR TELEPHONE EXCHANGES.

APPLICATION FILED JAN 14, 1902.

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1 fly I wmawz I v v Cifiorwgi Patented October 11, 1904.

UNITED STATES PATENT OFFICE.

WILLIAM W. DEAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO IVESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

CALL-SIGNAL APPARATUS FOR TELEPHONE-EXCHANGES.

SPECIFICATION forming part of Letters Patent No. 771,897, dated October 11, 1904. Application filed January 14:, 1902. Serial No. 89,661. (No model.)

To all whom, it may concern.-

Be it known that I, WILLIAM I/V. DEAN, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Call-Signal Apparatus for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description.

My invention relates to call-signal appara tus and circuits for telephone-exchanges, and has for its object to provide an improved form of calling or ringing key which when depressed to signal a telephone-substation will be held down and the ringing-current maintained upon the line until the subscriber at the station called for answers the calland which will automatically be released to remove the ringing-current from the line when the called party answers.

In the system of my invention the ringingkey at the central office is adapted when actuated to connect a source of signaling-current with the called line, and a magnet associated with the ringing-key is adapted to hold the key in its operative position, so that said key when once depressed will be held down by the magnet until released, independent of further manual operation by the switchboard attendant. Y 7

The principal feature of my invention consists in providing a neutralizing-winding for the sticking or retaining magnet which holds the key in its operative position and controlling the flow of current in the neutralizingwinding through the agency of a switch at the substation actuated in the use of the telephone, so that when the called subscriber takes his telephone from its hook the circuit which includes the neutralizing-winding of the sticking magnet will be supplied with current, whereupon the magnet, being thus denergized, will release the ringing-key and the ringing-current will thus be automatically removed from the line.

My invention consists, further, in certain details of construction of the ringing-key.

I will describe my invention particularly by reference to the accompanying drawings and that which I regard as new will be pointed out in the appended claims.

Figure 1 is a diagram illustrating by means Fig. 4 is a view from below.

. The same characters of reference are used to designate the same parts throughout the several figures.

Referring first to Fig. 1, the telephone-line extends in two limbs 1 2 from the spring-jack a at the central office to the substation A. At the substation the usual telephone-talking apparatus is provided in association with an ordinary gravity-telephone switch-hook 5 controlling the circuits through such apparatus. When the telephone-receiver 0 at the substation rests upon its hook, the circuit between the limbs l 2 of the telephone-line through the talking apparatus is broken, but when the telephone is removed from its hook the hook automatically closes the bridge of the line including thetelephone apparatus in the usual manner. The subscribers call-bell (Z is included serially with a condenser e in a bridge of the line conductors 1 2 at the substation. At the central office the operator is providedwith the usual pair of plugs and their plug-circuits for connecting any two telephone-lines together for conversation. A pair of plugs f g is shown in the drawings with the link conductors of a plug-circuit uniting them, the plug f being the answering-plug and the plug g the callingplug. A battery it is connected in a bridge of the plug-circuit between the windings of a repeating-coil and oneside of the battery. The side which is connected throughthe cordstrand 3 with the tip of the plug is grounded at it. The opposite pole of the battery is connected by a conductor 5 with the shank or third contact g of the connecting-plug through the winding 2" of the sticking-magnet which is associated with the ringing-key. A second I winding Z for the sticking-magnet is included in a conductor 6, extending from the segment Z of a continuously-rotating commutator Z to the back contact k of the ringing-key 7:. The ringing-key consists in its elements of two contact-springs in k connected, respectively, with the tip 9 and ring g of the connectingplug, normally resting contacts 73 Zr for said contact-springs,respectively, said resting-contacts being connected with poles of the battery it, and outer contacts It", against which the springs 76' 7:; are adapted to strike when the key is depressed. The outer contact la is grounded at h. The key is thus adapted when depressed to sever the plug-circuit between the battery and the connecting-plug and connect the severed ends thereof leading to the contacts g g of the plug with the metallic segment Z of the commutator Z and with ground, respectively. The commutator Z is divided into two segments, the segment Z whereof isconnected with the conductor 6, as before described, and the other segment is insulated or made of insulating material. Two brushes m a rest upon the commutator at opposite points, one of said brushes m being connected with the grounded generator 0 of alternating current and the other brush a being connected with a grounded battery or source of direct current In practice the battery 19 is identical with the battery /tthat is, the brush a is connected with one terminal of the battery it; but for convenience of illustration 1 have shown two separate batteries. The windings of the magnet are so connected, however, as tohave differential effects-that is, the current from battery 19 flows through windingt' in a direction to neutralize the effect of the current in the winding Z.

1 will now proceed to describe more in detail the mechanism of the ringing-key, directing attention to Figs. 2, 3, and 4. The switchsprings of the key are horizontally mounted in a block of insulating material q, secured to the under side of a rectangular metallic framework r. A bell-crank switch-levers is pivoted at s to this framework. The long horizontal arm 8 of the bell-crank switch-lever carries upon its end an iron armature s and a push-button 5*, mounted-to slide up and down in the framework 1*, straddles this arm 8 so that when the push-button is depressed the lever is rocked upon its pivot s. The lower or vertical arm s of the bell-crank switch-lever carries an insulating-wedge 8 When the lever is rocked upon the pivot, the wedge s is forced between the ends of the switch-springs 7c 76 and presses them apart so that they break contact with the anvils Z0 is and engage with the anvils 70 70*, respectively. Normally, however, the springs it" 70 pressing upon the wedge s, yieldingly maintain theswitch-lever in an elevated position, as shown in full lines in Fig. 2. The magnet 1; is mounted upon the under side of the framework 1', immediately below the armature 8 which is carried upon the end of the arm .9 This magnet is disposed vertically, as shown, and has an L- shaped pole-piece i secured to the lower end of the core and passing up alongside the magnet to the upper end thereof in position to en- 'gage the armature .9 A pair of terminal pieces or soldering-points 'Z Z is connected with one winding of the magnet, and the other pair of terminal pieces 2' i is connected with the neutralizing-winding of the'imagnet. The range of movement of the armature carried by the switch-lever is so great that when the switch-lever is in its normal elevated position the magnet, even if energized, would not have sufficient strength to draw it down; but when the switch-lever is pressed down by the pushbutton 8 the magnet if excited will cause the armature carried by the end of the switch-lever to stick to its pole-pieces, thus holding the lever. in a depressed position.

The provision of the bell-crank lever above described renders it possible to employ stiff switch-springs, which are very desirable in order to obtain firm and reliable electrical contacts. A comparatively weak lockingmagnet, moreover, may be used in connection with said lever, due to the mounting of the armature of the magnet upon the long arm of said lever, whereby very little power is required to hold said lever in its operative position. Furthermore, by the use of said bellcrank lever it becomes possible to obtain a vertical movement of the long arm carrying the push-button and a horizontal movement of the short arm carrying the wedge, permitting the mounting of the switch-springs in a horizontal plane and the magnet in a vertical plane. These features are of course very desirable in switchboard operation.

The operation of the system may be briefly traced as follows: When the operator inserts her connecting-plug g into the spring-jack (Z to make connection with the telephone-line of subscriber A, a local circuit of battery it is completed from ground through the conductor 5 and the winding i of the sticking-magnet to the shank g of the plug, and thence to the grounded test-ring or third contact a of the spring-jack a. This test-ring is connected to ground by the conductor 7, which includes the winding of the usual cut-off relay which is associated with each telephone-line in modern switchboards. The magnet 2' is thus energized by current in the circuit so established, and when the operator, desiring to signal the subscriber, depresses the push-button of the ringing-key the armature 8 sticks to the pole of the magnet, so that the ringing-key is maintained in its depressed or operative position until the magnet is deenergized. The depression of the ringing-key connects the segment Z of the commutator Z with the spring 70 and sowith the ring-contact of the connecting-plug, and grounds the other spring 70,

and contact if to ground at it.

which is connected with the tip of the plug. As the commutator Z rotates alternating current from the generator 0 is intermittently applied to the conductor 6 and flows through the winding 2' and to the ring-contact of the plug out over the limb 1 of the telephone-line to the substation, through the bridge, which includes the signal-bell and condenser, then back over the limb 2 of the line to the shorter line spring of the spring-jack to the tip of.

the plug, and thence by way of the spring In the intervals between the application of the alternating ringing-current the source of steady current p is applied to the conductor 6, but no current flows over the circuit until the called subscriber responds, since steady current cannot traverse the condenser e at the substation. The alternating current is so weakened by the high resistance of the callbell bridge at the substation that, although its efl'ect upon the magnet Z during a portion of its cycle of alternation is in a direction tending to neutralize the effect of the current from battery it, flowing through the winding c", yetthis neutralizing eflect is not strong enough to denergize the magnet sufiiciently to release the armature. When, however, the subscriber A answers the call by removing his telephone from its switch-hook Z), a low-resistance path for the current is provided at the substation through the telephone apparatus, and the ringing-current is so strengthened that at some period in its alternation it will cause an effect upon the magnet Z equal and opposite to the efiect produced by the current flowing in the winding Z, whereupon the armature s will be released and the key will assume its normal position, establishing the plug-circuit and cutting off the ringingcurrent from the line. The same effect will be produced if at the moment when the subscriber removes his telephone from its hook the commutator Z is in such a position that the source of steady current 10 is connected with the ringing-key instead of the source of alternating current, for the bridge at the substation through the telephone apparatus, closed' by the removal of the receiver from its hook, affords a low-resistance path for the direct current, and the battery 10 is connected so that current flows through the winding'Z in a reverse direction from the current in the winding 2'. The batteries h and p and the windings Z and 2' are so proportioned that the magnetic eflect of the current flowing in the winding 2' balances or neutralizes the effect of the current flowing in the other winding.

Having thus described my invention, I claim as new, and desire to secure by Letters Patcut, the following:

1. The combination with a telephone-line extending from a substation to a central oflice, of a call-bell at the substation and a switch for determining the flow of current in the line, a spring-jack for the line at the central oflice, an operators plug and plug-circuit for making connection with the line, a source of calling-current at the central oflEice, a callingkey in the plug-circuit for applying said source of calling-current to the line, a retaining-magnet adapted to hold the calling-key in its operative position when once actuated, said retaining-magnet having an energizing and a neutralizing winding, a circuit including the energizing-winding of the magnet, established in registering contacts of the plug and spring-jack in making connection with the line, and means, controlled through the agency of the switch at the substation, for sending current through said neutralizingwinding, as set forth.

2. The combination with a telephone-line extending from a substation to a central oflice, of a call-signal and a switch for determining the flow of current in the line at the substation, a calling-key at the central office, a retaming-magnet for said calling-key, adapted to hold the same in its operative position when actuated, a circuit 6 adapted to be connected with the line by the calling-key when actuated, a neutralizing-winding for the retainingmagnet included in said circuit 6, a source of alternating current 0 and a source of steady current 10, and a commutator Z adapted to connect said sources of current 0 9 alternately with the circuit 6, substantially as set forth.

3. In a ringing-key, the combination with the switch-springs, of a bell-crank lever and a push-button for operating the same, one arm of said bell-crank lever carrying a wedge for actuating the switch-springs of the key, an armature carried by the other arm of said bell-crank lever, and an electromagnet underneath said armature, adapted to engage the same when the bell-crank lever is rocked to actuate the switch-springs, substantially as set forth.

4. In aringing-key, the combination with the framework, of a bell-crank lever pivoted at one end of said framework and having a substantially horizontal arm adapted to move up and down within the framework, switchsprings operated by the other arm of said bell-crank lever, a push-button adapted to slide up and down in the framework, said push-button being connected with the horizontal arm of the bell-crank lever to operate the same, an armature carried near the end of said horizontal arm, and a magnet mounted upon the under side of said framework and arranged to hold the armature when depressed.

In witness whereof I hereunto subscribe my name this 7th day of November, A. D. 1900.

WILLIAM W. DEAN.

Witnesses:

DE Wrr'r C. TANNER, W. W. LEAGH. 

